Purification of water.



UNITED STATES PATENT OFFICE. ERNEST EDWARD MUNRO IPAYNE, 0F- LEICESTER, ENGLAND, ASSIGNOR 0F (DYE-HALF '.[0 WILLIAM HENRY STAYNES, 0F LEICESTER, ENGLAND.

rnmrxcmroir or WATER.

No JDrawi'ng.

matter, lime salts and other metallic salts,

such as carbonates of calcium and'magne- 'sium, sulfates, chlorid of calcium, magnesia,

iron, alumina, etc. It is a comparatively easy matter to get rid of the temporary hardness but'it is frequently diflicult to get rid of the permanent hardness completely According to this invention the permanent hardness is removed from water by the addition -of tri-sodium-phosphate (Na PO Preferably the temporary hardness is removed by the addition of suificient caustic soda to combine with all the carbonic acid existing as such or in the form of acid carbonates and adding tri-sodium-phosphate 3 00- Conveniently the precipitants are added simultaneously. These precipitants may be prepared b mixing common phosphate of soda (Na 0 with caustic soda so as to produce tri-sodium-phosphate (Na PO and to leave the desired amount of excess of free caustic soda in the mixturewhen dissolved in hot pure water, according to the equation:

The following is a description of. the methods of carrying this invention into effect.

A sample of the water is analyzed. The amount of caustic soda necessary to combine with all the carbonic acid existing as such or as acid carbonates is calculated according to the equations:

and a solution containing the caustic soda and. tri-sodium-phosphate is added to the Specification of Letters Patent. AppIication filed August 4,

Patented Sept. 5, 1911.

1909. Serial No. 511,166.

water which is then agitated. The reactions which occur may be stated as follows The water is then allowed to rest and estimated and found to be 4 parts per 100,000, according to the formula:

CaH 2(C'O,) 3MgSO, Fe,Gl A1 01 OaCl 2NaHO-I-GNa PO 202.00

+Mg 2(PO were, 2A1P0, 14. I

NaC1+ snaeso, 2H,0.

8?,- lbs. of solid phosphate of soda (Na,HPO,12H,O) is mixed with 4 lbs. of caustic soda solution sp. gr. 14.00-containing approximately 1% lbs. of caustic soda. These are dissolved in 10 gallons of hot purified water. At this stage wehave a solution of tri-sodium phosphate containing excess of caustic soda. This solution is poured into 1000 gallons of the impure water and the whole is agitated. After twelve to twenty hours settling. a pure water is decanted suiiiciently free as regards metallic contamination to be serviceable for manufacturing and other purposes, whereas the origina useless. a

By the usual chemical tests such as ammonium oxalate, etc., the purified water was found to be practically freed from the original obj ectionable contamination.

The sludge precipitate is run off through sludge cocks and is either dried and-used for its manurial value, or for the reparation of superphosphates for agricultural water was quite purposes. The sludge consists of mixed carbonates of calcium, magnesium, etc. (depending on the amount of carbonic acid and acid carbonates in the original water) and all the original suspended im urities and mixed phosphates of the meta s present in the original water. Certain of these phosphates are soluble in water containing carbonic acid but by the above process all the carbonic acid is removed and the phosphates are practically insoluble.

This invention has been described with the use of sodium salts but it is to be understood that similar salts of potassium, or ammonium may be vused alone or together if desired.

What I claim as my invention and desire to secure by Letters Patent is 1.- The herein described method of treating water, which consists in adding thereto a caustic alkali in a suificient quantity to combine with the carbonic acid and acid.

carbonates contained in the water, and also adding tri-sodium-phosphate, thereby forming normal phosphates of the metals held in solution in the water and causing their precipitation.

2. The herein described method of treating water, which consists in adding to the water a solution of tri-sodium-phosphate containing an excess of caustic soda, the soda being suflicient to combine with the carbonic acid and acid carbonates contained in the water; and the tri-sodium phosphate forming normal phosphates of. the metals in solution in the water and the precipitation thereof.

'3. 'The herein described method of treating water, which consists in adding caustic alkali to the water to combine with its contained carbonic acid and acid carbonates and also adding tri-sodium-phosphate, then agitating the water and allowin it to settle to allow normal phosphates of the metals held in solution to precipitate, and then decanting the clear water therefrom.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ERNEST EDWARD MUNRO PAYNE.

Witnesses:

Gno. MORGAN, WALTER H. Sronons. 

